In general, a glycosylated compound obtained by glycosylating a certain compound is likely to have improved stability and solubility compared with the corresponding unglycosylated compound. Therefore, glycosyl transfer reactions for glycosylation of various compounds have been actively studied. In addition, glycosyl transfer reactions can be applied to sugar chain synthesis. Thus, the glycosyl transfer reaction is one of highlighted research themes.
There is a known glycosyl transfer reaction observed in nature, which is involved in color development of plant petals or fruits. For example, Patent Literature 1 describes a method comprising incorporating a morning-glory-derived gene into a different plant so as to transfer glucose to sugar moiety of a flavonoid having the sugar at the 3 position, thereby providing a flower having a color different from a natural plant.
There are many known glycosyl transfer reactions in which a sugar nucleotide such as UDP-glucose is used as a sugar donor. For example, Non-Patent Literature 1 describes that UDP-glucose:anthocyanidin 5-glycosyltransferase derived from Japanese basil, verbena, or the like catalyzes a reaction of transferring a sugar to a hydroxy group at the 5 position of anthocyanidin with the use of UDP-glucose as a sugar donor. Non-Patent Literature 2 describes that UDP-glucose:flavonoid 3-glycosyltransferase from Japanese basil, maize (Zea mays), gentian, grape, or the like catalyses a reaction of transferring a sugar to a hydroxy group at the 3 position of flavonoid or anthocyanidin with the use of UDP-glucose as a sugar donor. Patent Literature 2 describes that an antirrhinum-derived enzyme catalyzes a reaction of transferring a sugar to a hydroxy group at the 4′ position of a chalcone with the use of UDP-glucose as a sugar donor. In addition, Patent Literature 1 describes that glycosyltransferase encoded by a gene incorporated therein catalyzes a reaction of transferring glucose with the use of UDP-glucose as a sugar donor (see Example 4 in Patent Literature 1).